PascalCompiler

• written in Java
• book used
  • Crafting a Compiler by Fischer Cytron and LeBlanc

How to Run

• javac Compiler.java
• java Compiler `source code`

Background

Compiler.java

- main program used to compile your Pascal source code

Lexer.java

- aka lexical analyzer, scanner, tokenzierr
- reads source code 1 char at a time and groups them into tokens
    - tokens are identifiers, integers, keywords, and delimeters
- eliminates unneeded info (like comments)
- Only Arithmetic and Relational Operators, no Bitwise or Boolean
- returns a list of tokens
- Notes:
    - used HashMap instead of HashTable because did not need thread synchroniziation
    - HashMap also allows for null 

keywords.txt

- list of pascal keywords the compiler understands
- [list used](https://www.freepascal.org/docs-html/ref/refsu1.html)

Token.java

- class to create objects that have a type and a value

Parser.java

- takes the encoded tokens (often as integers) for syntactic analysis
- understands the syntax of the language 
- creates a tree of nodes called the Abstract Syntax Tree (AST)
    - operators/operations are roots and interior nodes
    - operands are the children
- returns a list of ByteCode
- Grammar
    - [site info](http://homepage.divms.uiowa.edu/~jones/compiler/spring13/notes/10.shtml)

Optimizer.java

- for our purposes this was not used

SymbolTable.java

- (ADT) Abstract Data Type for Tracking Symbols in the Source Code
- [site info](http://www.cs.dartmouth.edu/~mckeeman/cs48/mxcom/doc/Symbols.html)

Generator.java

- Takes the Byte-Code from the Parser and Converts to Machine Instructions